The present invention relates to a method and a system for adjusting the descent trajectory of an aircraft, in particular of a transport aircraft.
It is known that modern aircraft have onboard systems which make it possible, with the help of performance data described below, to calculate a flight plan, as well as associated predictions, and to guide the aircraft so that it follows the calculated flight plan.
On certain aircraft, the performance data are not reset by flight tests for the descent phases during which the engines of the aircraft are operating in idling mode and can therefore exhibit differences with respect to the real performance of the aircraft when it is delivered. Moreover, these differences can increase with the degradation of the aerodynamics or the wear of the engines during the service life of the aircraft.
In this context, means must be developed in order to model the descent performance of the aircraft as accurately as possible. As the performance data are notably used during a descent for determining the position of the start of descent point, a low quality model can give rise to a descent that is to early or too late, which can hamper the pilot's operation, give rise to thrust increases or to deployment of air brakes during the descent and to an overall excess fuel consumption.
New generation flight management systems, of the FMS (Flight Management System) type, generally comprise a functionality that allows the adjustment of the descent profiles and the predictions associated with these profiles, using for this purpose a value called an adjustment parameter. This functionality is able to vary the performance of the aircraft on both the descent and approach profiles.
However, this adjustment parameter depends on the type of the engines but not on the real capabilities of the aircraft.